Fluid pumps with increased pumping efficiency

ABSTRACT

A fluid pump includes a piston disposed within a compartment and defining therewith a fluid-charging chamber on one side of the piston and a fluid-pumping chamber on the opposite side of the piston. The piston is formed with an opening therethrough establishing communication between the chambers. A one-way valve carried by the piston is effective to close the opening through the piston during the forward-pumping strokes and to open the opening during the return strokes. Further valve means are provided effective: to open the inlet with respect to the fluid-charging chamber during the forward-pumping strokes, to close the inlet with respect to the fluid-charging chamber during the return strokes, to open the outlet with respect to the fluid-pumping chamber during the forward-pumping strokes, and to close the outlet with respect to the fluid-pumping chamber during the return strokes. The arrangement is such that during the return strokes, pressurized fluid from the fluid-charging chamber flows through the opening through the piston into the fluid-pumping chamber to thereby supercharge the fluid-pumping chamber before the start of the forward-pumping strokes.

FIELD AND BACKGROUND OF THE INVENTION

[0001] The present application relates to fluid pumps. The invention is particularly useful in fluid pumps for pumping air or other gases, and is therefore described below with respect to this application, but it will be appreciated that the invention could also be used for pumping water or other liquids.

[0002] Fluid pumps are widely used for many applications, including moving fluids from one location to another (translation pumps), compressing the fluid within a container (compression pumps) and reducing the pressure of a fluid within a container (vacuum pumps). Efforts are continually being made to increase the pumping efficiency of such pumps for reducing the power requirements, to make the pumps more compact for reducing the space requirements, and/or to simplify the structure of the pumps for reducing the manufacturing and maintenance costs.

OBJECTS AND BRIEF SUMMARY OF THE PRESENT INVENTION

[0003] An object of the present invention is to provide a fluid pump having advantages in one or more of the above respects, as will be described more particularly below.

[0004] According to one aspect of the present invention, there is provided a fluid pump, comprising: a housing having an inlet, an outlet, a passageway connecting the inlet and outlet, and a compartment in the passageway; a piston disposed within a compartment and defining therewith a fluid-charging chamber on one side of the piston and a fluid-pumping chamber on the opposite side of the piston; the piston being reciprocatable in the compartment through forward-pumping strokes and return strokes; the piston being formed with an opening therethrough establishing communication between the chambers and including a one-way valve effective to close the opening through the piston during the forward-pumping strokes and to open the opening during the return strokes; and further valve means effective: to open the inlet with respect to the fluid-charging chamber during the forward-pumping strokes, to close the inlet with respect to the fluid-charging chamber during the return strokes, to open the outlet with respect to the fluid-pumping chamber during the forward-pumping strokes, and to close the outlet with respect to the fluid-pumping chamber during the return strokes; such that during the return strokes, pressurized fluid from the fluid-charging chamber flows through the opening through the piston into the fluid-pumping chamber to thereby supercharge the fluid-pumping chamber before the start of the forward-pumping strokes.

[0005] A fluid pump constructed in accordance with the foregoing features is to be distinguished from other types of fluid pumps also including one-way valves through their pistons, such as described in Hammond U.S. Pat. No. 883,457. For example, in the fluid pump of the present invention the fluid-charging chamber at one side of the piston is expanded during the forward-pumping strokes, and is contracted during the return strokes to pressurize the fluid within that chamber and thereby, by the opening of the piston valve, to supercharge the fluid-pumping chamber before the start of the forward-pumping strokes. In the fluid pump of Hammond, however, the fluid charging chamber (8) is not expanded during the forward-pumping strokes, but rather is contracted during the forward-pumping strokes, and is expanded during the return strokes. Moreover, the inlet one-way valve (6) is normally closed during the forward-pumping strokes, rather than during the return strokes, unless that valve is held open by presetting a cam (17). Such differences in structure in the Hammond pump produce a different operation from that of the fluid pump of the present invention, as will be described more particularly below.

[0006] According to still further features in one described preferred embodiment, the volume of the fluid-pumping chamber is greater than that of the fluid-charging chamber. For this purpose, the piston stem is located in the fluid-charging chamber and occupies a part of the volume of that chamber.

[0007] Other embodiments are described wherein the volume of the fluid-pumping chamber is less than that of the fluid-charging chamber. This can be done by providing the piston with a cylindrical section of smaller diameter than the piston and located in the fluid-pumping chamber such that the effective volume of the fluid-pumping chamber is less than that of the fluid-charging chamber.

[0008] The latter embodiments of the invention are particularly useful in applications requiring a relatively high outlet pressure. It will be appreciated, however, that other techniques can be used for dimensioning the relative volumes of the two chambers as desired, particularly for reducing the volume of the fluid-pumping chamber in order to increase the outlet pressure, such as using a stepped piston, as described for example in Weinhandl U.S. Pat. No. 4,657,488.

[0009] According to further features, the housing of the fluid pump includes a linear drive for reciprocating the piston through the forward and return strokes. Particularly advantageous results are obtainable when the drive is the linear electromagnetic drive described in my International Application No. PCT/IL02/00313, filed 18 Apr., 2002, Published ______, as International Publication No. ______. The embodiments of the invention described below therefore include such a drive.

[0010] As will be described more particularly below, fluid pumps constructed in accordance with the foregoing features are capable of operating at relatively high efficiency, thereby reducing the power requirements. They are also capable of being implemented in compact constructions, thereby reducing the space requirements. Further, they are capable of being constructed of a relatively few simple parts which can be produced in volume and at relatively low cost, thereby reducing the manufacturing and maintenance costs.

[0011] Further features and advantages of the invention will be apparent from the description below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:

[0013]FIG. 1 is a longitudinal sectional view illustrating one form of fluid pump constructed in accordance with the present invention;

[0014]FIGS. 2a, 2 b and 2 c illustrate the reciprocatory movements of the armature of the linear electromagnetic drive in the fluid pump of FIG. 1;

[0015]FIG. 3 is a diagram illustrating how an increase in efficiency is obtainable in a fluid pump constructed in accordance with the present invention as compared to a typical prior art construction;

[0016]FIG. 4 is a longitudinal view illustrating a two-stage fluid pump constructed in accordance with the present invention;

[0017]FIG. 5 is a longitudinal sectional view illustrating a third fluid pump constructed in accordance with the present invention; and

[0018]FIG. 6 is a longitudinal sectional view illustrating a still further fluid pump constructed in accordance with the present invention.

[0019] It is to be understood that the foregoing drawings, and the description below, are provided primarily for purposes of facilitating understanding the conceptual aspects of the invention and various possible embodiments thereof, including what is presently considered to be a preferred embodiment. In the interest of clarity and brevity, no attempt is made to provide more details than necessary to enable one skilled in the art, using routine skill and design, to understand and practice the described invention. It is to be further understood that the embodiments described are for purposes of example only, and that the invention is capable of being embodied in other forms and applications than described herein.

THE FLUID PUMP OF FIGS. 1-3 Overall Construction

[0020]FIG. 1 illustrates one form of fluid pump constructed in accordance with the present invention. As indicated above, particularly advantageous results are obtainable when such a fluid pump includes a linear electromagnetic drive of the construction described in my above-cited International Patent Application No. PCT/IL02/00313, and therefore such a drive is included in the fluid pump illustrated in FIG. 1. The operation of such a drive will be better understood by reference to FIGS. 2a-2 c described below. The advantages obtainable by such a fluid pump will be better understood by reference to the diagrams of FIG. 3, also described below.

[0021] The fluid pump illustrated in FIG. 1 includes a housing, generally designated 2, constituted of a section 2 a for housing a linear electromagnetic drive, and a section 2 b for housing the pump valving elements driven by the electromagnetic drive.

The Linear Electromagnetic Drive Section 2 a

[0022] The linear electromagnetic device section 2 a includes: a core 3 of magnetically permeable material; a coil 4 wound on a bobbin 5 fixed within the core 3; and an armature 6 of magnetically permeable material mounted for bi-directional reciprocatory movement towards and away from one end face of the core 3.

[0023] The bi-directional movements of the armature 6 are transmitted as linear movements by a shaft 7 passing through the core 3 to a piston 8 at the opposite side of the device. Piston 8 is movable within a cylindrical compartment defined by two transverse walls 9, 10 of the fluid valving section 2 b, such that the reciprocations of the piston 8 produce an air pumping action as will be described more particularly below.

[0024] Armature 6 and its shaft 7 are supported for bi-directional linear movement by a pair of a flat elastic springs 13, 14, of disc configuration at the opposite sides of core 3 and connected to the core by a pair of side plates 15, 16 secured together by axially extending tie rods or long screws 17. As more particularly described in the above-cited International Application, each flat spring is made of elastic sheet material of a circular disc shape and formed with a plurality of coaxial circular arrays of closed, elongated curved slots to impart axial flexibility while providing transverse (radial) stiffness.

[0025] Piston 8 is secured to one end of shaft 7 by a fastener 18 which passes through the piston and the respective flat spring 13 at that side of the core. The opposite end of shaft 7 is secured to flat spring 14 by another fastener 19 passing through it and an outer collar 19 a.

[0026] As particularly shown in FIG. 1, the core 3 of magnetically permeable material has a longitudinal axis LA, an outer section 3 a of cylindrical configuration coaxial with axis LA; a central section 3 b coaxial with axis LA, spaced from the outer section 3 a, and also of cylindrical configuration; and a side section 3 c, perpendicular to axis LA, bridging the other cylindrical section 3 a and the central cylindrical section 3 b at one side of the core (left side, FIG. 1). The opposite side (right side, FIG. 1) of the core is not bridged, but rather is left open. The right side of the core 3 is extended past the coil 4 and bobbin 5, as shown at 3 d. Coil 4 and bobbin 5 are both spaced inwardly of the open side of the core so as to be completely recessed within the core and to define an annular recess, shown as 20.

[0027] The movable armature 6 faces and is aligned with extension 3 d defining the annular recess 20 within core 3. Armature 6 is movable towards and away from the coil 4 and its bobbin 5 inwardly and outwardly of the annular recess 20. The outer diameter of armature 6 is slightly less than the inner diameter of the outer core section 3 a at the annular recess 20. The armature is formed with a central recess 6 a of slightly larger diameter than the outer diameter of the central core section 3 b to define an outer annular section 6 b of the armature receivable within the annular recess 20 of the core 3 during the reciprocatory movement of the armature.

[0028] Coil 4 is energized by a source of alternating current 30 having a half-wave rectifier 31 effective to energize the coil in half-cycles to drive the armature 6 in one direction, and to de-energize the coil in the remaining half-cycles to permit the pair of flat springs 13, 14 to drive the armature in the opposite direction.

[0029] The operation of the electromagnetic device section 2 a of housing 2 will be better understood by referring to FIGS. 2a-2 c illustrating three positions of the armature 6 with respect to the core 3, as the armature is driven in one direction by the coil during one-half of each cycle, and in the opposite direction by the flat springs 13, 14, during the other half of each cycle. Such reciprocatory movements are straight-line movements parallel to the longitudinal axis LA of the core 3.

[0030]FIG. 2a illustrates the initial or normal position (i.e., at the working point) of the armature, also shown in FIG. 1, when coil 4 is deenergized. In this initial position of the armature 6 as illustrated in FIG. 2a, the outer annular section 6 b of the armature is aligned with the annular recess 20 defined by the outer core section 3 a, the central core section 3 b, the recessed coil 4 and its bobbin 5.

[0031]FIG. 2a illustrates this initial position of the armature as being substantially flush with the outer face of the central core section 3 b. However, this depends on the working point of the electromagnetic device. In some applications the initial position of the armature may be slightly inwardly, and in other applications slightly outwardly, of the outer face of central core section 3 b.

[0032]FIG. 2b illustrates the maximum inner position of the armature with respect to the core; and FIG. 2c illustrates the maximum outer position of the armature with respect to the core.

[0033] As best seen in FIG. 2b, the outer surface of the armature annular section 6 b which, as described earlier, is of only slightly smaller diameter than the inner diameter of the core outer section 3 a, defines a first working gap WG1 with the inner surface of the outer section 3 a of the core. Similarly, the inner surface of the armature annular section 6 b, bordering the central recess 6 a for accommodating the core central section 3 b, defines a second working gap WG2 with the outer surface of the core central section 3 b. Both gaps WG1, WG2 are working gaps, in the sense that they change in dimension during the bi-directional, reciprocatory movements, of the armature 6, and thereby contribute to the attractive force produced by the magnetic flux flowing through the core 3. In this embodiment both working gaps WG1, WG2 are of annular configuration.

[0034] As also best seen in FIG. 2b, there are two magnetic flux loops MF1, MF2 through the core 3 and armature 6. Each loop includes the two gaps WG1, WG2. Both gaps change in length during the movement of the armature 6 as shown in FIGS. 2a and 2 c, and therefore serve as working gaps contributing an attractive force with respect to the armature. The provision of two working gaps in each circulating loop of magnetic flux maximizes the mechanical force produced by the device for the electrical power consumed.

[0035] It will thus be seen that in the initial position of armature 6, as illustrated in FIG. 2a, the electromagnetic force applied to the armature is at a maximum, whereas the spring force applied to the armature is at a minimum. As the armature moves inwardly within recess 20, the electromagnetic force decreases because of magnetic saturation, whereas the spring force increases by the loading of the spring. When the innermost position of the armature is reached, as shown in FIG. 2b, the electromagnetic force is minimum and the spring force is maximum. The spring force then moves the armature outwardly to the outermost position shown in FIG. 2c. Here again the spring force is maximum tending to move the armature back towards the recess 20 to the initial position illustrated in FIG. 2a, wherein the spring force is minimum but the electromagnetic force is maximum. The electromagnetic force thus complements the spring force to produce an efficient reciprocity movement of the armature.

[0036] It will also be seen that the reciprocatory movements of the armature 6, and thereby of the shaft 7 and the piston 8, are linear straight-line movements parallel to the longitudinal axis LA of the core 3. Such straight line reciprocatory movements produce a more efficient pumping action than angular movements resulting from a pivotally-mounted armature, thereby further maximizing the mechanical force produced by the device for the electrical power consumed.

[0037] It will be further seen that since the coil 4 and its bobbin 5 are both fixed in core 3 and recessed with respect to the side of that core facing the armature 6, it is not necessary to provide fixed gaps, i.e., gaps which do not change in length during the movement of the armature 6. As indicated earlier, such fixed, or non-working, gaps are generally provided in electromagnetic devices to accommodate manufacturing tolerances with respect to relatively movable surfaces. Since the structure illustrated in FIGS. 1 and 2a-2 c eliminates the need for fixed gaps, it minimizes the fringe flux, that is, flux lines which do not pass through a working gap. As result, the illustrated construction eliminates the energy loss associated with driving flux through a non-working gap, thereby minimizing power consumption as well as heat generation. Further, the absence of an air space (a non-working gap) between the coil and the core produces better heat dissipation of the heat generated in the coil.

[0038] A further advantage is that, since no fixed (non-working) gap is required between the coil of the core and the armature, the coil may be of smaller diameter for the same number of turns, thereby decreasing the overall length of the coil wire; alternatively the wire diameter may be slightly increased for the same overall diameter of the core. Either case enables the resistance of the coil wire to be reduced, thereby further contributing to the reduction in the power consumed and the heat generated.

[0039] In addition, non-working gaps are generally provided in existing electromagnetic devices in order to accommodate manufacturing tolerances with respect to relatively movable surfaces during the operation of the armature. Such non-working gaps tend to produce undesirable side forces according to the degree of eccentricity with respect to the relatively movable surfaces. Since non-working gaps are not needed in the above-described construction illustrated in FIGS. 1 and 2a-2 c, such side forces may be substantially eliminated, so that the electromagnetic device operates more efficiently and with less wear of the parts thereby, contributing to longer life.

The Valving Section 2 b

[0040] The valve elements producing the fluid-pumping action are located within the valving section 2 b defined by the two transverse plates 9, 10 which define a cylindrical compartment within which piston 8 reciprocates. Piston 8 is disposed within this compartment, or cylinder, so as to define therewith a fluid-charging chamber C_(C) on one side (right side, FIG. 1), and a fluid-pumping chamber C_(P) on the opposite side. Piston 8 is reciprocated by shaft 7 through forward-pumping strokes (leftwardly, FIG. 1) and return strokes to produce the fluid-pumping action, as will be described more particularly below.

[0041] Piston 8 is formed with at least one opening 40 therethrough, preferably a plurality of openings as shown in FIG. 1, establishing communication between the two chambers C_(C) and C_(P) on opposite side of the piston. Each of the piston openings 40 includes a one-way valve V_(P) effective to be closed during the forward-pumping strokes and to be opened during the return strokes.

[0042] Transverse plate 9 defining the opposite side of the fluid-charging chamber C_(C) is also formed with at least one opening 41 therethrough, preferably a plurality of such openings, each controlled by a one-way valve so as to control the inletting of fluid into the fluid-charging chamber C_(C); such one-way valves act as inlet valves and are therefore designated V_(I). Similarly, transverse plate 10 defining the opposite side of the fluid-pumping chamber C_(P) is also formed with at least one opening therethrough 42, preferably a plurality of such openings, each controlled by a one-way valve to control the outletting of fluid from the fluid-pumping chamber C_(P); such one-way valves act as outlet valves and are therefore designated V_(O).

[0043] The cylinder defined by the two transverse walls 9, 10, in which piston 8 is reciprocateable, is in a connecting passageway between a fluid inlet to the housing, and a fluid outlet from the housing. In the construction illustrated in FIG. 1, the housing fluid inlet, designated 43, is at the right side of the housing and is constituted of the elongated curved slots formed in flat spring 14 at that end of the housing. The connecting fluid passageway from inlet 43 to the fluid-charging chamber C_(C) includes openings 44 through the armature 6, and an annular passageway 45 between shaft 7 and core 3. Passageway 45 communicates with inlet openings 41 via the elongated curved slots in flat spring 13 at that (left) side of the electromagnetic drive section 2 a of housing 2.

[0044] In the construction illustrated in FIG. 1, the fluid outlet from housing 2 is defined by an opening 46 through an outer transverse plate 47 attached to transverse wall 10. Plate 47 defines with wall 10 a further chamber C_(D), serving to dampen the pressure pulsations and sounds of the fluid flowing from the pumping chamber C_(P) through openings 42 and outlet 46 during the forward-pumping (leftward) strokes of the piston 8.

[0045] As shown in FIG. 1, the three groups of one-way valves, V_(P), V_(I) and V_(O), are oriented to operate as follows: The piston one-way valves V_(P) close the piston openings 40 during the forward-pumping (leftward) strokes of the piston, and open openings 40 during the return (rightward) strokes. The inlet one-way valve V_(I) open the path from the inlet 43 to the fluid-charging chamber C_(C), via armature openings 44, annular passageway 45 and openings 41, during the forward-pumping strokes of the piston, and close this path during the return strokes. The outlet one-way valves V_(O) open the path from the fluid-pumping chamber C_(P) to the housing outlet 46, during the forward-pumping strokes of the piston, and close this path during the return strokes of the piston.

[0046] As will also be described more particularly below, such an arrangement enables pressurized fluid to flow from the charging chamber C_(C) into the pumping chamber C_(P) during the return strokes, to thereby supercharge the fluid-pumping chamber C_(P) to a higher pressure before the start of the forward-pumping strokes.

[0047] While FIG. 1 schematically illustrates the one-way valve V_(P), V_(I), V_(O) as being simple flapper valves, it will be appreciated that they could be any type of one-way valve, such as an umbrella valve, inertia valve, ball valve, etc.

Operation

[0048] As described earlier, the electromagnetic drive section 2 a of the illustrated fluid pump reciprocates piston 8 through forward-pumping strokes (leftwardly, FIG. 1) and return strokes (rightwardly) with respect to the fluid-charging chamber C_(C) and the fluid-pumping chamber C_(P).

[0049] During a forward-pumping stroke, piston 8 moves leftwardly to close one-way valve V_(P) and to open one-way valves V_(O) and V_(I). During this stroke, the piston pumps the fluid from chamber C_(P) through valves V_(O) and the housing outlet 46, while at the same time it draws fluid via opening 41 into the fluid-charging chamber C_(C).

[0050] During the next return strokes, piston 8 moves in the opposite direction, i.e., rightwardly, FIG. 1. At the beginning of such movement, fluid-pumping chamber C_(P) is immediately expanded, thus causing valve V_(O) to immediately close; in addition, the fluid-charging chamber C_(C) is immediately contracted, thereby causing valve V_(I) to immediately close.

[0051] With respect to valve V_(P), this valve, is in a closed condition at the beginning of the return stroke, but opens during the return stroke according to the pressure on its opposite faces and the biasing pressure, if any, biasing it closed. As soon as valve V_(P) opens during the return stroke, pressurized fluid within the fluid-charging chamber C_(C) passes into the fluid-pumping chamber C_(P) thereby boosting the pressure within the fluid-pumping chamber C_(P) before the start of the next forward-pumping stroke.

[0052] It will thus be seen that, by charging the fluid-charging chamber C_(C) during the forward-pumping strokes, and passing pressurized fluid from the fluid-charging chamber C_(C) to the fluid-pumping chamber C_(P) during the following return stroke, the fluid-pumping chamber C_(P) is supercharged before the start of the next forward-pumping stroke.

[0053]FIG. 3 is a diagram illustrating the pressure-volume relationship with respect to a fluid pump constructed in accordance with the present invention (curve A) as compared to that of a conventional fluid pump (curve B) not having a supercharged pumping chamber. The displacements illustrated in FIG. 3 are adjusted to produce 3.4 cfm at 3600 cycles per minute. In this example, the fluid pump constructed in accordance with the present invention (curve A) supercharges the fluid-pumping chamber C_(P) at about two psig (16.5 psia, assuming no leakage) when the fluid pump is at 20 psig back pressure.

[0054] A pump constructed in accordance with the foregoing features provides a number of important advantages. Thus, a linear reciprocatory drive is generally not as advantageous in a pump as a constant-displacement drive because of the need for more “dead volume” in a linear drive in order to avoid the danger of impact of the piston against the valve plate. However, in the pump constructed in accordance with the present invention, the use of a linear reciprocatory drive is particularly advantageous since here the “dead volume” effectively increases the super-charging effect. Moreover, with such a drive, leakage is not significant at the piston stem, thereby avoiding the need of a seal at the piston stem and the friction produced by such a seal. Further, all the valves, particularly the suction valves, are disposed within the housing, thereby reducing noise. In addition, the opening of the piston valves during the return strokes not only supercharges the fluid-pumping chamber before the start of the fluid-pumping stroke as described above, but also reduces the load during the return stroke. Further, the fluid being pumped is passed through the interior of the reciprocatory drive, thereby cooling that drive.

[0055] It will thus be seen that a fluid pump constructed in accordance with the features illustrated in FIG. 1 is capable of attaining higher efficiency, and therefore of reducing the power requirements. In addition, such a fluid pump may be constructed very compactly, thereby reducing the space requirements. Further such a fluid pump can be constructed of relatively few simple parts producible in volume and at relatively low cost, thereby reducing the manufacturing costs.

EXAMPLES OF OTHER EMBODIMENTS OF THE INVENTION The Embodiment of FIG. 4

[0056]FIG. 4 illustrates a two-stage fluid pump, generally designated 100, constructed in accordance with the present invention. The pump illustrated in FIG. 4 includes a housing having an electromagnetic linear drive coupled at one end to a first valving section 2 b ₁, and at the opposite end to a second valving section 2 b ₂. The drive section 2 a is constructed exactly as described above with respect to FIG. 1, and therefore the same reference numerals have been used to identify it and its corresponding parts, with the subscripts “1” and “2” for the two valving sections “b1” and “b2”, respectively.

[0057] As shown in FIG. 4, shaft 7 of the reciprocatory drive section 2 a is coupled at one end to a first piston 8 ₁ in valving section 2 b ₁, and at the opposite end to a second piston 8 ₂ in valving section 2 b ₂.

[0058] As further shown in FIG. 4, each of the two valving sections 2 b ₁, 2 b ₂ is of the same construction as valve section 2 b in FIG. 1; and therefore to facilitate understanding, the various parts have also been identified with the same reference numerals but with the subscript “1” and “2”, respectively. Thus, the one-way valves in valving section 2 b ₁ are identified as V_(I1), V_(P1), V_(O1), and the various chambers are identified as C_(C1), C_(P1), and C_(D1); whereas the corresponding elements in valving section 2 b ₂ are identified as V_(I2), V_(O2), C_(C2), C_(P2) and C_(D2).

[0059] It will be seen from FIG. 4 that the one-way valves in the two sections 2 b ₁ and 2 b ₂ are oriented such that valving section 2 b ₁ constitutes a first stage of the pump, and valving section 2 b ₂ constitutes a second stage of the pump. Thus, during the leftward stroke of the shaft 7, both pistons 8 ₁ and 8 ₂ are driven leftwardly. The leftward movement of piston 8 ₁ draws air into chamber C_(C1) via inlet 19 ₁, and also pumps air out of chamber C_(D1) via the openings in the disc spring 14 and opening 41 ₂ into the charging chamber C_(C2) of the second valving section 2 b ₂, thereby supercharging the air within that chamber. During the rightward movement of piston 8 ₁, its pumping chamber C_(P1) is supercharged from its fluid-charging chamber C_(C1) in the same manner as described above with respect to FIG. 1.

[0060] Valving section 2 b ₂ operates in the same manner as described above with respect to FIG. 1, except that in this case its fluid-charging chamber C_(C2) is supercharged by the pressurized fluid within the pumping chamber C_(P1) of the first valving section 2 b ₁ at the start of the leftward-moving pumping stroke of piston 8 ₂.

[0061] It will thus be seen that valving section 2 b ₂ of the pump illustrated in FIG. 4 operates in the same manner as described above with respect to FIG. 1, except that its fluid-charging chamber C_(C2) is supercharged by the fluid pumped from valving section 2 b ₁. Thus, valving section 2 b ₁ acts to supercharge the air supplied to valving section 2 b ₂ before section 2 b ₂ further supercharges the air pumped therefrom in a manner as described above with respect to FIG. 1.

[0062] While FIG. 4 illustrates the cylindrical chambers of the two pistons 8 ₁, 8 ₂, as being of the same diameter, preferably piston 8 ₂ of the second stage 2 b ₂ is of smaller diameter since that stage acts on fluid at a higher pressure than the fluid in the first stage.

[0063] Another minor modification illustrated in the fluid pump illustrated in FIG. 4 is that, instead of having a plurality of one-way valves for each of the two sections 2 b ₁, 2 b ₂, there is only one such one-way valve in each of the two sections.

The Embodiment of FIG. 5

[0064] The operation of the fluid pump illustrated in FIG. 5, therein generally designated 200, is basically the same as described above with respect to FIG. 1. Its electromagnetic drive section is the same, and therefore corresponding parts have been identified with the same reference numerals. Its fluid-valving section involves the same basic operation as fluid-valving section 2 b in FIG. 1 but of a slightly different construction. To facilitate understanding, therefore, the corresponding parts in the fluid-valving section of the fluid pump 200 illustrated in FIG. 5 are identified by the same reference numerals as in FIG. 1, but in the “200” series.

[0065] As in the fluid pump illustrated in FIG. 1, the piston 208 in fluid pump 200 illustrated in FIG. 5 is also coupled to shaft 7 of the reciprocatory drive section 2 a for reciprocation within a cylindrical compartment, and also divides the compartment into a fluid-charging chamber C_(C) and fluid-pumping chamber C_(P). In this case, however, piston 208 includes a cylindrical section 250 of smaller diameter than that of the piston and located within the fluid-pumping chamber C_(P) such that the effective volume of that chamber is less than that of the fluid-charging chamber C_(C).

[0066] Pump 200 illustrated in FIG. 5 is otherwise of basically the same construction as in FIG. 1, including one-way valve V_(P) in piston 208, one-way valve V_(I) in housing wall 209, and one-way valve V_(O) in housing wall 210. In FIG. 5, the fluid inlet is shown at 219, and the fluid outlet is shown at 246.

[0067] It will be seen that fluid pump 200 illustrated in FIG. 5 operates in basically the same manner as described above with respect to FIG. 1 except for the following principle difference: Since the volume of the fluid-pumping chamber C_(P) is reduced by the cylindrical section 250 of the piston 208 during the return strokes of the piston, when pressurized fluid flows from the fluid-charging chamber C_(C) into the fluid-pumping chamber C_(P) via valve V_(P), the fluid-pumping chamber will be supercharged to a greater extent than in FIG. 1 before the start of the forward-pumping strokes.

[0068] It will be noted that transverse wall 248 in FIG. 5, formed with the inlet opening 219, defines an inlet chamber C_(DI) communicating with the fluid-charging chamber C_(C) for damping the sounds of the inletted fluid, and that circumferential wall 247 formed with the outlet opening 246, defines an outlet chamber C_(DO) communicating with the fluid-pumping chamber C_(P) for damping the pressure pulsation's and sounds of the outletted fluid.

The Embodiment of FIG. 6

[0069]FIG. 6 illustrates a fluid pump, therein generally designated 300, which is similar to that of FIG. 5, including a cylindrical section, therein designated 350, carried by the piston 308 coaxially therewith and located within the fluid-pumping compartment C_(P) so as to reduce the volume of that compartment as compared to the volume in the fluid-charging chamber C_(C). In this case, however, the piston 308 is coupled to shaft 7 of the electromagnetic drive section 2 a at one side of the piston, and carries the coaxial cylindrical section 350 at the opposite side of the piston. Transverse wall 347 formed with the outlet opening 346 defines an annular outlet chamber C_(D) communicating with the fluid-pumping chamber C_(P) for damping the pressure pulsations and sounds of the outletted fluid. This arrangement permits the fluid outlet 346 of the fluid pump to be located in transverse wall 347 of the housing, rather than in circumferential wall 247 of the housing in the FIG. 5 construction.

[0070] Fluid pump 300 illustrated in FIG. 6 otherwise is constructed and operates substantially the same as described above with respect to FIGS. 1-5.

[0071] While the invention has been described with respect to several preferred embodiments, it will be appreciated that these are set forth merely for purposes of example, and that variations may be made. For example, each of the flat springs 13, 14 could be, and preferably is, a stack of such springs rather than a single spring. In addition, the one-way valves illustrated could be of any appropriate construction, inertia valves being particularly preferable in the illustrated fluid pump. Further, the pump could be used for pumping liquids as well as gases. Moreover, the invention could be implemented in a vacuum pump, e.g., by reversing the inlet and outlet or reversing the locations of the valves.

[0072] Many other variations, modifications and applications of the invention will be apparent. 

What is claimed is:
 1. A fluid pump, comprising: a housing having an inlet, an outlet, a passageway connecting said inlet to said outlet, and a compartment in said passageway; a piston disposed within said compartment and defining therewith a fluid-charging chamber on one side of the piston and a fluid-pumping chamber on the opposite side of the piston; said piston being reciprocatable in said compartment through forward-pumping strokes and return strokes; said piston being formed with an opening therethrough establishing communication between said chambers, and including a one-way valve effective to close said opening during the forward-pumping strokes and to open said opening during the return strokes; and further valve means effective: to open said inlet with respect to said fluid-charging chamber during said forward-pumping strokes, to close said inlet with respect to said fluid-charging chamber during said return strokes, to open said outlet with respect to said fluid-pumping chamber during said forward-pumping strokes, and to close said outlet with respect to said fluid-pumping chamber during said return strokes; such that during said return strokes, pressurized fluid from said fluid-charging chamber flows through said opening through the piston into said fluid-pumping chamber to thereby supercharge said fluid-pumping chamber before the start of said forward-pumping strokes.
 2. The fluid pump according to claim 1, wherein said compartment is of cylindrical configuration.
 3. The fluid pump according to claim 1, wherein said piston further includes a cylindrical section of smaller diameter than said piston and located in said fluid-pumping chamber such that the effective volume of said fluid-pumping chamber is less than that of said fluid-charging chamber.
 4. The fluid pump according to claim 1, wherein said piston includes a plurality of said opening therethrough, and a said one-way valve for each of said openings.
 5. The fluid pump according to claim 1, wherein said further valve means comprises: a second one-way valve effective to open said inlet with respect to said fluid-charging chamber during said forward-pumping strokes, and to close said inlet with respect to said fluid-charging chamber during said return strokes; and a third one-way valve effective to open said outlet with respect to said fluid-pumping chamber during said forward-pumping strokes, and to close said outlet with respect to said fluid-pumping chamber during said return strokes.
 6. The fluid pump according to claim 5, wherein said second one-way valve and said third one-way valve are carried by said housing.
 7. The fluid pump according to claim 6, wherein said housing includes a plurality of said second one-way valves and a plurality of said third one-way valves.
 8. The fluid pump according to claim 1, wherein said housing outlet is formed axially through a transverse wall of said housing.
 9. The fluid pump according to claim 1, wherein said housing outlet is formed radially through a circumferential wall of said housing.
 10. The fluid pump according to claim 1, wherein said housing further includes an inlet chamber communicating with said fluid-charging chamber for damping the pressure fluctuations and sounds of the inletted fluid, and/or an outlet chamber communicating with said fluid-pumping chamber for damping the pressure fluctuations and sounds of the outletted fluid.
 11. The fluid pump according to claim 1, wherein said pump is a two-stage pump, including a first stage at one end of said housing and constructed as defined, and a second stage at the opposite end of the housing and of the same construction as said first stage; the fluid-pumping chamber of said first stage communicating with the fluid-charging chamber of said second stage such that, during each forward stroke of the pump, fluid from the fluid-pumping chamber of the first stage is pumped into the fluid-charging chamber of the second stage.
 12. The fluid pump according to claim 1, wherein said housing further includes a linear drive for reciprocating said piston through said forward-pumping and return strokes.
 13. The fluid pump according to claim 11, wherein said drive is an electromagnetic linear drive coupled to said piston to reciprocate it through linear forward-pumping and return strokes.
 14. The fluid pump according to claim 13, wherein said electromagnetic linear drive comprises: a core of magnetically permeable material having a longitudinal axis, a central section coaxial with said longitudinal axis, an outer section spaced outwardly from said central section, and a bridging side section bridging the outer and central sections at one side of the core, the opposite side of the core being open; a coil in the space between said central and outer sections of said core and spaced inwardly of the open side of the core such that the coil is completely recessed within the core, and the outer and central sections of the core define an extension extending laterally past the recessed coil; a movable armature of magnetically permeable material facing and aligned with said extension in the core, said armature being movable towards and away from said coil and being formed with a central recess; and a pair of springs on the opposite ends of said core and coaxial with the longitudinal axis of the core, said pair of spring mounting said armature for straight-line reciprocatory movements parallel to said longitudinal axis of the core; said armature and its recess being configured and located such that during the movement of the armature towards and away from the coil: (a) the recess receives said central section of the core; (b) the outer surface of the armature defines a first working gap with the inner surface of the core outer section at said extension; (c) and the inner surface of the armature at said recess defines a second working gap with the outer surface of the core central section at said extension.
 15. A fluid pump, comprising: a housing having an inlet, an outlet, a passageway connecting said inlet to said outlet, and a compartment in said passageway; a piston disposed within said compartment and defining therewith a fluid-charging chamber on one side of the piston and a fluid-pumping chamber on the opposite side of the piston; said piston being reciprocatable in said compartment through forward-pumping strokes and return strokes; said piston being formed with an opening therethrough establishing communication between said chambers; a drive for reciprocating said piston through said forward and return strokes; a first one-way valve, carried by said piston, effective to close said opening through the piston during said forward-pumping strokes and to open said opening during said return strokes; a second one-way valve effective to open said inlet with respect to said fluid-charging chamber during said forward-pumping strokes, and to close said inlet with respect to said fluid-charging chamber during said return strokes; and a third one-way valve effective to open said outlet with respect to said fluid-pumping chamber during said forward-pumping strokes, and to close said outlet with respect to said fluid-pumping chamber during said return strokes; the arrangement being such that, during said return strokes, pressurized fluid from said fluid-charging chamber flows through said opening through the piston into said fluid-pumping chamber to thereby supercharge fluid-pumping chamber before the start of said forward-pumping strokes.
 16. The fluid pump according to claim 15, wherein said housing further includes a linear drive for reciprocating said piston through said forward-pumping and return strokes.
 17. The fluid pump according to claim 15, wherein said housing outlet is formed axially through a transverse wall of said housing.
 18. The fluid pump according to claim 15, wherein said housing outlet is formed radially through a circumferential wall of said housing.
 19. The fluid pump according to claim 15, wherein said piston further includes a cylindrical section of smaller diameter than said piston and located in said fluid-pumping chamber such that the effective volume of said fluid-pumping chamber is less than that of said fluid-charging chamber.
 20. The fluid pump according to claim 15, wherein said pump is a two-stage pump, including a first stage at one end of said housing and constructed as defined, and a second stage at the opposite end of the housing and of the same construction as said first stage; the fluid-pumping chamber of said first stage communicating with the fluid-charging chamber of said second stage such that, during each forward stroke of the pump, fluid from the fluid-pumping chamber of the first stage is pumped into the fluid-charging chamber of the second stage. 